"Today, we have been experiencing delays in the reporting of your AdWords account statistics. This delay is temporary and does not affect the serving of your ads as per your campaign settings.

We have been working hard to get this fixed, and at this time, click and cost statistics have been updated and show the correct numbers. Correct impression counts will follow soon. As a result of these reporting delays, your clickthrough rate (CTR) may show a higher than actual number until the impression counts are also updated. This delay in reporting is unrelated to the ads quality improvements that we wrote about on Monday. We regret any inconvenience that this may cause you and appreciate your patience as we work toward a resolution."

http://adwords.blogspot.com/2008/11/delay-in-updating-campaign-statistics.html